The present invention relates to poppet valves and in particular to ball poppet valves which are generally known from the prior art and are employed as directional control valves or shutoff valves having a freely movable ball poppet as a shutoff element. Ball poppet valves are distinguished by simplicity of construction and a high degree of freedom from leakage and are therefore very well suited to many applications.
In a ball poppet valve according to the prior art, control action is achieved in that an annular flow area A established by lifting of a control stem between a ball poppet and a control edge on the valve aperture is smaller than the maximal flow area Amax bounded by the control stem and the valve bore. However, because this flow area between the ball poppet and the control edge reaches the maximal flow area Amax when the ball poppet is lifted even very slightly, adequate control action can not be achieved with ball poppet valves according to the prior art.
A problem with prior art ball poppet valves is that, because of their structural form, they enable a relatively large flow when the ball poppet is lifted even a small amount off the valve aperture. Electromagnetically actuated ball poppet valves for example exhibit a large flow for even a small current flowing in an exciter coil. In electromagnetically controlled ball poppet valves of the kind identified above, this relationship manifests itself in a steep Q-I characteristic (flow-current characteristic) and has the disadvantage that only slight control of the flow is possible with such a ball poppet valve.
Gate valves are also known wherein the ports are connected to or separated from one another by a sliding element, the so-called gate. The movement of the gate here can be axial or rotational, a flow control action being achieved with individual chambers or channels. Gate valves are characterized by good control behavior and, in the example of electromagnetic actuation, by a flat Q-I characteristic. Such gate valves have the disadvantage that 100% freedom from leakage cannot be achieved because of manufacturing tolerances and the functional construction of the valves.
There is a need for a ball poppet valve that exhibits both a high degree of freedom from leakage and a configurable control characteristic. In the case of electromagnetically actuated ball poppet valves in particular, the flow-current characteristic should be adjustable over a wide range.